Volume control means for variable density sound recording



y 1936- I E. H. HAEs EN 2,041,470

VOLUME CONTROL MEANS FOR VARIABLE DENSITY SOUND RECORDING Filed April 12, 1930 I5 Sheets-Sheet l scum) RECORDING SLIT FOG TUBE l4 FOG v su'r f I REMOTE CONTROL DIAL mimocx CONTROL (SOUND TUBE RECORDI UT GLOW TUBE INVENTOR.

May 19, 1936. E. H. HANSEN VOLUME CONTROL MEANS FOR VARIABLE DENSITY SOUND REOORDING Filed Apiil 12, 1950 s Sheets-Sheet 2 11v VENIOR smhzou v ATTORNEY E. H. HANSEN May 19, 1936.

VOLUME CONTROL MEANS FOR VARIABLHDENSITY SOUND RECORDING Filed April 12, 1930 5 Sheets-Sheet 3 mmvzmmm Q30 .rzam x21 m Us)? JJMU OFOIL 20 F103 INVENTOR TTORNEY Patented May 19, 1936 I PATENT OFFICE VOLUME CONTROL MEANS FOR VARIABLE DENSITY SOUND RECORDING Edmund H. Hansen, Los Angeles, Calif. Application April 12, 1930, Serial No. 443,711

5 Claim.

This invention has reference to the art of recording and reproducing sound waves, and particularly relates to the process of recording vibrations of audible frequencies upon a sensitive fllm and reproducing such audible frequencies under control as to volume without'change in present equipment, or the addition thereto, thus adapting standard equipment for sound projection machines to the purposes and functions of my invention.

It is known that the average volume range in film recording is 32 db. and is accomplished by varying the input of speech currents to the electro-light translation device, such as the light valve, glow tube, Kerr cell, etc. The term decibel is a decimal of the bel which is defined as follows. Two powers are said to differ by one bel or ten decibels (db.) when the larger power is tens times greater than the other. This may be stated in a generalized way by the following equation:

- P at 810 If it is desired to use'a current or a voltage rather than power, the following equation may be used:

provided it is stated that the respective currents and voltages are associated with identical impedanees. In the above:

P=power V=voltage i=current.

This volume range is further extended, during reproduction, by 'means of a variable attenuation pad, called a iader", which varies the output of the amplifier system. This variable attenuator is manually actuated from a predetermined cueing sheet. Another means of varying the sound output is to vary the illumination of the sound exciting lamp which passes through an optical system and the film and falling on the photo-electric cell to be converted into speech currents, which are further amplified by the speech amplifying system. These methods of volume control require a means of rheostat control such as notched iiim, selector relays, and the necessary interconnecting magnetic controi of the exciting-lam 2 rheostat.

inasmuch the amount at high photo-electric cell is a function of the intrinsic value of the source, the width of sound track, the width and length or the focused light beam, and the density of the film, I have found it to be possible to accomplish volume control by varying 5 the width of the sound track, and this without the addition of equipment to standard sound projection machines.

My invention consists in the apparatus by medium of which I accomplish my results in both recording and reproducing; and the ultimate result disclosed herein is one wherein the active sound track width is varied by the introduction of a fog exposure eiectro-mechanically operated, the same being opaque to transmission of light Objects of importance and the functional results of the apparatus embodying my present invention, will be set forth in detail during the course of this description, and in the claims I will state the important features of the apparatus and 20 combinations of elements constituting my invention.

In order that my invention may be clearly understood, I have provided drawings wherein:

Figure 1 is a plan view of a section of film showing the relative position of the picture fractions, sound track the relation of the sound recording slit of the sound tube, and that portion of the volume control means which embodies the fog slit, which modifies the functions of the 30 striatic structure of the film resulting from the vibrations of audible frequencies;

Figure 2 is a view showing in sectional elevation a sound recording camera with my invention applied thereto, and with the wiring diagramatically 35 arranged;

Figure 3is a schematic view of the wiring of my system of means, showing how my method of automatic volume control is carried out;

Figure 4 is a view similar to Figure 3 showing a simple form. of reproducer and how reproduction is carried out;

Figure 5 is a diagrammatic view showing the lamp, lens and width gate of reproducing apparatus in proper juxtaposition with reference to the film; and

Figure 6 is a plan view of a section of the film, showing how the striations of vibrations of audible frequencies arefogged under automatic control. 50

Figures 4 and 5 should he read together, and the him of Figure 5 is shown between the two figures in edgewise position, which is the operative rellation of the same to reproducing apparams.

Figure 7 shows another schematic form of winding for the interlocked motors shown in Figure 3.

tive film for moving picture purposes now well known in the art, the margins of which are provided with the usual feed slots or apertures 2, and between said slots are the fractional picture frames 3 of a predetermined subject, it being understood that in the treatment and production of the film the latter is fed in the direction of the arrow. According to my invention, I make the film I considerably wider than usual or sufficiently wider to enable the production thereon of sound striations, the record of which may be either a single, vertical striatic path, or a helical record as set forth in my copending application Ser. No. 235,526, filed Nov. 25, 1927 which has eventuated into Patent No. 1,857,451 issued May 10, 1932. This path or record, of whatever form, is indicated at 4 and, according to my invention, is located between one of the sets of marginal feed slots and a vertical edge, or longitudinal edge, of the fractional picture frames; and according to my invention this striatic record is coordinated with the fractional picture frames so as to bring about perfect synchronization of the function of sound vibrations and recordation of the photographic subjects-matter. In order that my invention may be clearly understood, I have also shown in Figure 1 the relative position of the sound recording slit" of the recording instrument, and also the relative position of the "fog tube and the slit thereof which befogs the sound striations of the record, as indicated at 5.

In Figure 2 the sound recording camera is indicated at 6 and the casing 1 contains the delivery reel 8 on which the film i is wound and also the take-up reel 9 upon which the treated him is rewound or taken up after the sound tube and recording glow tube have performed their functions in combination with the sound recording slit upon the film. The arrow in Figure 2 within the camera 6 indicates the direction of feed of the film from their-eel 8 to the reel 8. Conveniently within the camera, but at a point between the sound tube slit and the tal e-up reel 9, I introduce a fog-tube ID, the latter with its slit being indicated by legend. A feed sprocket or gulderoll II is interposed in the path of movement of the film around which the latter is fed in proper relation to the sound tube slit and recording tube. The function of my fog-tube is to befog or becloud all or a portion of the sound striations 4, as indicated at 5, in Figures 1 and 6, thus controlling as need be, or to the extent desired, the efl'ective width of the sound track. This function of my device is produced by making the fog-tube slit of a size approximately twice the width or length of the sound-tube slit. Thus it will be observed, with reference to Figures 1 and 6, that the sound recording slit, having laid down a striatic diagram of the sound record, as at I, the fllm is caused to pass under, or relatively to, the volume control fog-tube slit. Should the fog slit in the tube [0 lie parallel to the recording slit, or the said striations I, as indicated by the solid lines i2, Figure 1, a log is producelii of the same width as the sound track, which produces an opaque track in a positive print that allows no light to fall upon the photo-cell in the sound projection system. The indicated at I2. Rotation of the fog-tube to the position indicated by the diagonal dotted lines I3 will produce a control fog-track of the width indicated at [3; and the further rotation of the fog-tube will cause its slit indicated, for example, by dotted lines I to create a control fog-track oi. the width indicated at H. From this it will be understood that any number of fog-track control positions may be brought about by shifting the fog-tube l0, thus producing any volume control eifect which may be desired.

The adjustment of the fog-tube and the control of its operation may be brought about by any suitable mechanical means an example of which is shown in Figure 2 embodying my remote con trol dial. In Figure 2, the mounting of the fogtube in the sound recording camera is indicated at l 5, the said tube being mounted in the hub of a worm-wheel IS, in mesh with a worm I! on the shaft of a synchronizing motor IS, in circuit with a similar motor l9, under control of the remote control dial 2B. the hand of which rotates a worm wheel 2| which drives a worm 22 carried by the shaft 23 of the synchronizing motor 19. Thus, regardless of the location of the control means 20, the remote control motor 15 may be caused to electrically control the motor it, thus causing the fog tube to be rotated and its slit arljusted as may be desired or required. The log tube has its lamp in a circuit, the energizing medium of which is indicated at 24, and current regulating means or rheostat at 25. In the circuit 26 the glow tube 2'! is inserted, being located in the fog-tube. Conveniently, the synchronizing motor I8 is mounted on the recordingv camera, and both the motors i8 and i9 are the three-phase type having a common source of stator excitation. By shifting the rotor of either motor, a similar angular displacement of the other will be brought about, their synchronous rotation as motors being prevented by the introduction of a control resistor in the rotor circuit.

In the operation of the above apparatus, it will be noted that with the fog-tube in the position indicated at 12, Figure 1, the track is entirely belogged. This would be the position of the tube during silent intervals and would eliminate all ground noise. As the tube is rotated, as indicated by the position of the slit at i 3, the track width will be increased, as indicated at I3; and a still greater increase in the track width may be brought about by adjusting the fog-tube as indicatcd at M thus producing the increased track "width l4. Variations are brought about through the medium of the synchronizing motors under control of the remote control dial. Thus, it will be understood that under the adjustments noted, there is a variation in the track width and cone sponding light falling on the photo-cell with an increase in volume above that when using the lllm in the standard manner. In the theater reproducing equipment, the volume control iader system is set on a point above that used with the normal uncontrolled track width. This point is one which gives the same sound output with the restricted track, as previously obtained with the full width track. As certain amounts of restrictions are removed, there is an increase of track width with an increase in volume above that when using the film in standard manner.

In addition to the remote controlmeans defog-track thus produced is scribed in the foregoing, I may also insert, in shunt to the synchronized motors l8 and IS, an interlock control of the motors, said control means being provided with usual rheostat regulation, as indicated at 28.

In practice, it has been found possible to extend the volume range of film recording by my method by approximately fourteen decibels, which increases the average film recording system from approximately 32 decibels to forty-six decibels, this range being sufficient for volume from a whisper to the roar of a cannon. And it will be also apparent that my method and apparatus may be used to control the entire volume range by keeping the recording slit modulated at an optimum point and varying the opaque track width from zero to full width.

In Figure 3, I have laid out diagrammatically and according to conventional signs the circuit of the apparatus shown in Figure 2. In, Figure 3 the reference characters and printed iridicia are the same as in Figure 2. From this diagram it will be seen that the remote control mechanism can be at any distant point, in the theater, or house, or other place where the film is being made with its synchronized subjects-matter. In Figure 3, the sound recording camera has been omitted for clarity, and due to the limitations of the sheet; but, its relative arrangement and juxtaposition can easily be determined by reference to the fog tube which is mounted thereon in the relation described, and as shown in Figure 1. The energizing current for the apparatus, or system of means, may be derived from any suitable source; but, preferably, I utilize a source of three-phase, alternating current. In the drawings, Figure 3, I have shown, merely for demonstration in the system, the star or Y system of connection in the threephase, alternating current circuit. I do not wish to be confined to this form of connection, however, since I can use, and show for the purpose in Figure '7, the delta or mesh connection for the purpose of producing equal balance as to load in the three-phase circuit. As a matter of preference, I use the delta connection and have found it to give satisfaction. In Figure 'l the similar parts are designated by the same reference characters; but, the primary or stator coils are indicated at 30 and the secondary or rotor coils at 3 I.

In Figure 6, I have shown the film which has been produced, by the recording system of means shown in Figure 2, and adjacent thereto a graphic representation of sound volume plotted against effective track width and current output. Here it will be observed, that the sound volume is a linear response to variations in effective track width and that the sound volume may be controlled from zero to resulting from befogging the sound tract, or sound striations, under control of my fog-tube mechanism. In Figures 4 and 5, the film of Figure 6 is shown in edgewise position between the photo-cell and amplifier mechanism of a simple reproducer'and the optical head of the latter. The reproducer is shown in diagram, or schematically, and the important parts thereof are verbally indicated, and the several circuits for the lamp, photo-cell and amplifier will be readily understood. It will thus be seen that, as the befogged film is fed through the reproducer, the characteristics thereof will be faithfully reproduced in point of audibility synchronously with the reproduction of the visualized subject-matter, the audible subject-matter being heard synchronously and in perfect relation, under control as to volume, while the picture subjects-matter are projected upon the screen. 1 From the foregoing it will be seen that I have produced a new film or one having thereon, in addition to the usual record, the indications of vibrations of audible frequencies produced at the time of making the frames of the fractional subject-matter of the picture, the sound striations, resulting from the audible frequencies, being befogged in such manner under control that the width of the sound track is properly varied. Such control includes the width and length of the focussed light beam, and the density of the film, by merely varying the width of the sound track. Thereby I have accomplished automatically complete control of the volume of the vibrations of audible frequencies.

In addition, I have disclosed a mechanism, or system of means, by which control of the volume of audible frequencies can be brought about automatically by the mere adjustment of a dial at any remote point, or at any point desired by the operative who is either making a record on the film or reproducing such record.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A system for befogging longitudinal portions of a variable density sound track comprising: a light slit, and remote control means for rotating said slit to expose variable widths of said track to light from said slit.

2. A system for befogging longitudinal portions of a variable density sound track comprising: a rotatable light slit adapted to transmit light to said track, and means for rotating said slit to befog longitudinal portions of said track.

3. A system for befogging longitudinal portions of a variable density sound track comprising: a rotatable light slit adapted to transmit light to said track, and means under remote control for optionally rotating said slit to befog longitudinal portions of said track.

4. A system for varying the effective width of a variable density sound track comprising: a rotatable light slit adapted to transmit light to said sound track, and means for manually rotating said slit to befog longitudinal portions of said track.

5. A system for varying the effective width of a variable density sound track comprising: a rotatable light slit adapted to transmit light to said track, and means for arbitrarily rotating said slit to befog longitudinal portions of said track. EDMUND H. HANSEN. 

